Abstract : The decision to write a thesis on American involvement in Vietnam stems from a personal belief that widespread ignorance of the process by which the United States became involved is a basic cause of the controversy that had developed over Vietnam. Unlike World War II, the American people have not been presented with a sudden threat to their security which called for a total patriotic response. As in the case of Korea, there has been no Pearl Harbor incident in Vietnam to cause the public to rally round the flag or to accept unquestioningly the necessity of fighting a war in Asia. Consequently, the causes for the present conflict are unclear and it is this lack of clarity that has led to much of the doubt concerning the validity of American involvement in South Vietnam. The thesis recounts the historical development of American foreign policy in Vietnam from 1945 until 1960. Primary consideration is given to the political motivation behind the critical decisions made in 1950 and 1954 which were to create the legacy of involvement. In considering the consequences of these decisions, the discussion is limited to that of cause and effect. Little attempt is made to analyze the correctness of the policy followed.